The frequency shift can be detected using lockin techniques [1]}, [2]}, [3]}, [4]}. In some experiments, such as in pulsed magnetic fields, it is more straightforward to observe the free oscillation of the cantilever in the time-dependent magnetic field. [4]} Here we discuss some general properties of the oscillating cantilever relevant to such measurements. The free evolution of the cantilever in a slowly changing environment is described by
\(\frac{d^2∆θ}{dt^2} +ω_0(t)^2∆θ =0 \,,\) 
